Watching too much television could shorten your life, a study suggests. Research carried out in Australia, and published in the British Journal of Sports Medicine, showed that every hour of TV watched after the age of 25 may shorten lifespan by 22 minutes.

According to one of the report's authors, Dr Lennert Veerman, from the School of Population Health at the University of Queensland, it puts long hours spent in front of the box "in the same ballpark as smoking and obesity". "While smoking rates are declining, watching TV is not, which has implications at a population level," he said.

Last year, another Australian study found an hour of TV a day led to an 8% increase in the risk of premature death.

"We've taken that study and translated it into what it means for life expectancy in Australia given how much TV we watch," said Veerman.

Australians watch about two hours of TV a day. As a result their life expectancy at birth is reduced by 1.8 years for men and 1.5 years for women, according to the study. Britons watch more than three hours of TV a day, according to the Broadcasters' Audience Research Board.

Too much sitting, as distinct from too little exercise, is associated with higher mortality risk, particularly from cardiovascular disease. "Logically we know that physical activity is good for health and so it's not so strange that the reverse is not so good," said Veerman.

The report was based on an observational survey conducted in 1999-2000 with more than 11,000 participants aged 25 and over. Participants reported the amount of time they spent watching TV or videos in the previous week, when it was their main activity (ie, not doing the cooking or the ironing at the same time).

The report also showed that a person who watches an average of six hours of TV a day would live on average 4.8 years less than someone who watches none.